This application claims priority from German Application No. 101 09 479.5 filed on Feb. 28, 2001.
The invention relates to a piston-rod-less linear drive comprising a housing, which possesses a tube body delimiting a piston receiving space and provided at its ends with housing covers, such tube body being provided at one point on its periphery with a longitudinal slot permitting the passage therethrough of a force transmitting member able to be moved in the longitudinal direction of the slot, and a band arrangement extending along the longitudinal slot for closing the longitudinal slot, such band arrangement being composed of an inner closure band provided at the inner slot opening associated with the piston receiving space and/or of an outer closure band provided at the outer face of the tube body, the respective closure band being secured at its two terminal sections by securing means to the housing.
Such a piston-rod-less linear drive is for example disclosed in the European patent publication 0 715 083 B1.
It possesses a housing with a tube body of elongated shape, which delimits a piston receiving space, which is shut off by housing covers mounted on the tube body. The tube body is provided with a longitudinal slot extending along its length, which permits the passage of a force transmitting member moving in the longitudinal direction of the slot, such member being kinematically coupled with a piston able to be moved by fluid power and arranged in the piston receiving space. In order to prevent escape of the actuating fluid necessary for the actuation of the linear drive from the piston receiving space through the longitudinal slot an inner closure band is arranged at the inner slot opening, such inner closure band as a rule being termed a sealing band. Furthermore, at the outer slot opening an outer closure band is provided preventing the ingress of dirt, such outer band being generally in the form of a cover band. The two closure bands are moved clear of the longitudinal slot in the vicinity of the force transmitting member in order to render possible the passage of the same. At their two terminal sections of the bands they are respectively secured to the housing by securing means.
The attachment to the housing of the terminal sections of the closure bands is ensured in the linear drive of the said European patent publication 0 715 083 B1 by means of a clamping part biased at the terminal sections against the tube body. The terminal sections are screwed to such clamping part. In the case of this type of attachment on the basis of frictional engagement only there is the danger of the band arrangement made up of the two closure bands becoming detached from the band making up the band arrangement so that the sealing function is impaired. Moreover, the securing means occupy the terminal sections of the longitudinal slot, something which reduces the available overall length or, respectively, increases the overall length necessary for a desired working stroke.
The U.S. Pat. No. 4,555,980 discloses attachment of the terminal sections of the closure bands on the housing covers mounted terminally on the tube body. This means that the longitudinal slot in the tube body has a greater working length. However, this design does suffer from the disadvantage that the housing covers are only able to be attached and detached if the closure bands are unfixed at the same time, something that impedes handling during manufacture and later servicing operations.
Accordingly one object of the present invention is to provide a piston-rod-less linear drive in the case of which the attachment of the band arrangement takes place in a manner rendering possible compact dimensions and a simple assembly and disassembly of the linear drive.
In order to attain such aim there is a provision such that the securing means for the one or both band terminal sections of the inner and/or outer closure band comprise a support body arranged on the respective terminal band section, such support body projecting laterally past the outer face of the respective closure band and bearing against the associated terminal face of the tube body independently of the housing cover provided on the same terminal face.
Accordingly the attachment of the respective closure band takes place clear of the longitudinal slot and in a manner independent of the housing covers. The available working length of the longitudinal slot formed in the tube body is accordingly not reduced by the securing means and as a rule no extra machining of the tube body is required to produce the securing means. The cover mounted on the respective terminal side may be mounted and dismounted without taking off the band securing means, something which more particularly means a simplification of repairs servicing operations.
Further advantageous developments of the invention are defined in the dependent claims.
In principle it would be possible to utilize the securing means in accordance with the invention both in the case of linear drives provided with only one closure band and also in the case of linear drives having two closure bands on only one end of the tube body and to have a conventional securing means at the opposite end. A design is however particularly advantageous in the case of which the respective closure band is secured at both terminal band sections in the manner in accordance with the invention.
If the linear drive possesses a plurality of closure bands, there is then the possibility of securing same in each case by means of individual support bodies or by means of a common support body on the respective terminal face of the tube body. The separate design facilitates replacement when there is a defect, because the closure band which is not defective may remain in place. The common attachment on one and the same support body more particularly renders possible more rational production and more especially is useful when the support body has to perform other tasks as well.
Such a further task may for example be supporting components or an end-of-stroke damping means, with which the linear drive is fitted. A centering function is advantageously possible as well, if the support body is provided with a centering section, which plunges with a close fit into the opening, provided on the respective terminal face, in the piston receiving space.
The securing means do not interfere with any planned mounting of housing covers. A housing cover may accordingly be still directly mounted on the end of the tube body, if it is provided with a recess, into which the components, extending past the tube body at the end, of the band arrangement and out from the support body or bodies may plunge. There is more especially the possibility of having the recess in the form of a well at the mounting face, facing the tube body, of the housing cover so that the securing means are completely covered over.
Although it would in principle be possible to have a screw securing means with an interlocking effect between the terminal sections of the band and the associated support body, it is preferred to have a clamp securing means, in the case of which a transversely extending through hole is then not necessary. This is best ensured by a clamp securing means. The support body may have a socket for each closure band to be held, into which socket the terminal section of the band is inserted, the desired clamping effect being obtained for example by a wall section, deformed after insertion of the terminal band section, of the socket or by a clamping screw acting on the terminal band section and arranged on the support body.
The measures in accordance with the invention are applicable to a every piston-rod-less linear drive, that is to say for example even in the case of an electrical linear drive, there being particular advantages in the case of linear drives operated with fluid power and more particularly compressed air.
The following provides a detailed account of the invention with reference to the accompanying drawings